Baghdad  (AP) — A wave of car bombs struck Shiite pilgrims in several cities across Iraq on Wednesday, killing at least 65 people and wounding more than 200 in one of the deadliest attacks since U.S. troops withdrew from the country.

The bloodshed was a stark reminder of the political tensions threatening to provoke a new round of sectarian violence that once pushed Iraq to the brink of civil war. Nobody immediately claimed responsibility for the attacks, but they bore the hallmarks of Sunni insurgents who frequently target Shiites in Iraq.

Wednesday's blasts were the third attack this week targeting the annual pilgrimage that sees hundreds of thousands of Shiites converge on Baghdad to commemorate the 8th century death of revered Imam Moussa al-Kadhim, who is interred in a shrine in the northern neighborhood of Kazimiyah.

Most of the 16 separate explosions that rocked the country targeted the Shiite pilgrims, but two hit offices of political parties linked to Iraq's Kurdish minority. Authorities had tightened security ahead of the pilgrimage, including a blockade of the mainly Sunni area of Azamiyah, which is near the twin-domed Shiite shrine.

The level of violence has dropped dramatically in Iraq since peaking in 2006-2007 as the country faced a Sunni-led insurgency and retaliatory sectarian fighting that broke out after the U.S.-led invasion that ousted Saddam Hussein.

But political divisions have only deepened, paralyzing the country since the Americans withdrew all combat troops in mid-December.

Shiite Prime Minister Nouri al-Maliki has been accused of trying to monopolize power, and tensions spiked after Vice President Tariq al-Hashemi — the highest-ranking Sunni in Iraq's leadership — was charged with running death squads. The government began his trial in absentia since al-Hashemi was out of the country, drawing allegations the charges were part of a vendetta by the Shiite-led government.

The political stagnation has set back hopes for stability in Iraq and stalled efforts to rebuild the country after eight years of U.S. occupation.

Baghdad military command spokesman Col. Dhia al-Wakeel said the attacks were intended to reignite all-out sectarian bloodshed, "but Iraqis are fully aware of the terrorism agenda and will not slip into a sectarian conflict."

The first bomb struck a procession at around 5 a.m. in the town of Taji, north of Baghdad, killing seven people and wounding two others, two police officers said.

That was followed by four more morning blasts that hit other groups of pilgrims across the capital, killing 25 people and wounding more than 70, according to police and health officials.

South of Baghdad, two car bombs exploded minutes apart at dawn in the center of the city of Hillah, killing 21 people and wounding 53, according to two police officers and one health worker.

A parked car bomb also exploded near a group of pilgrims in the Shiite holy city of Karbala, 90 kilometers (55 miles) south of Baghdad, at about 8 a.m., killing two people and wounding 22 others, a police official and health official said.

Two nearly simultaneous car bombs also killed seven pilgrims and wounded 34 in the Shiite town of Balad, 80 kilometers (50 miles) north of Baghdad, , a police official and health official said.

All the officials spoke on condition of anonymity because they weren't authorized to release the information.

Another person was killed in the northern city of Kirkuk when three more bombs exploded, one of them outside the political office of a prominent ethnic Kurdish leader.

In the northern city of Mosul, a car bomb targeted an office of President Jalal Talabani's Patriotic Union of Kurdistan, killing two and wounding four others. Two other explosions elsewhere in Mosul wounded five people elsewhere in Mosul, about 360 kilometers (225 miles) northwest of Baghdad.

It was the deadliest day in Iraq since Jan. 5, when a wave of bombings targeting Shiites killed 78 people in Baghdad and outside the southern city of Nasiriyah.